Intelligent CSMA-based opportunistic spectrum access: Competition and cooperation

This paper presents a CSMA-based opportunistic spectrum access for secondary users (SUs) from a game-theoretic perspective. A key requirement for efficient design of CSMA-based access schemes for SUs is to address competition among SUs. Thus, to enable contention control in consideration of competition among SUs, an adaptive SU access approach based on a modified CSMA scheme is presented in which each SU accesses multiple idle frequency-slots of a licensed frequency band with different probabilities. The problem of finding optimal access probabilities of SUs is cast in a game-theoretic framework to highlight the issues of competition and cooperation among SUs. Subsequently, the existence, uniqueness and efficiency of Nash Equilibrium (NE) are investigated. To improve the efficiency of the unique NE in the competitive design, the game is transformed into a more cooperative framework exploiting a pricing mechanism. Finally, an algorithm based on the best response dynamics is developed in which each SU independently updates its access probabilities until convergence to the unique NE.